之前的文章中我们通过两种方式分别实现了描边效果，他们各有优缺点，也比较简单，今天我们来通过后期处理这种方式来实现描边效果，相对于之前两种实现方式要稍微复杂一点。
后期处理的描边最终效果图如下：
实现大致思路：
首先我们添加一个额外的摄像机用来专门渲染需要描边的对象，通过设置摄像机的LayerMask即可，然后将摄像机的Render Target设置为我们设定好的一张Render Texture上，设置如下：
然后在渲染之前（可以通过Unity内置的方法OnPreRender处理），通过一个纯色shader来处理该Render Texture，使其变为纯色，如下图
关键代码如下：
然后我们通过均值模糊或者高斯模糊来处理该RenderTexture，使其模糊 膨胀，然后和模糊之前的RenderTexture相减即可得到轮廓图。如图所示：
此时得到了轮廓图之后就好办了，直接和原图叠加即可得到最终的效果图
本篇文章采用了高斯模糊（参考了《Unity Shader入门精要》书中的高斯模糊）来处理RenderTexture，
高斯模糊也可以参考这里
最终代码如下：
Shader：
// Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'// ---------------------------【后处理-描边】---------------------------Shader "lcl/screenEffect/outLine"{// ---------------------------【属性】---------------------------Properties{_MainTex ("Texture", 2D) = "white" {}}// ---------------------------【子着色器】---------------------------SubShader{CGINCLUDE#include "UnityCG.cginc"sampler2D _MainTex;half4 _MainTex_TexelSize;float _BlurSize;sampler2D _BlurTex;sampler2D _SrcTex;fixed4 _OutlineColor;// ---------------------------【高斯模糊】---------------------------struct v2f{float4 pos : SV_POSITION;half2 uv[5]: TEXCOORD0;};//垂直方向的高斯模糊v2f vertBlurVertical(appdata_img v) {v2f o;o.pos = UnityObjectToClipPos(v.vertex);half2 uv = v.texcoord;o.uv[0] = uv;o.uv[1] = uv + float2(0.0, _MainTex_TexelSize.y * 1.0) * _BlurSize;o.uv[2] = uv - float2(0.0, _MainTex_TexelSize.y * 1.0) * _BlurSize;o.uv[3] = uv + float2(0.0, _MainTex_TexelSize.y * 2.0) * _BlurSize;o.uv[4] = uv - float2(0.0, _MainTex_TexelSize.y * 2.0) * _BlurSize;return o;}//水平方向的高斯模糊v2f vertBlurHorizontal(appdata_img v) {v2f o;o.pos = UnityObjectToClipPos(v.vertex);half2 uv = v.texcoord;o.uv[0] = uv;o.uv[1] = uv + float2(_MainTex_TexelSize.x * 1.0, 0.0) * _BlurSize;o.uv[2] = uv - float2(_MainTex_TexelSize.x * 1.0, 0.0) * _BlurSize;o.uv[3] = uv + float2(_MainTex_TexelSize.x * 2.0, 0.0) * _BlurSize;o.uv[4] = uv - float2(_MainTex_TexelSize.x * 2.0, 0.0) * _BlurSize;return o;}//高斯模糊片段着色器fixed4 fragBlur(v2f i) : SV_Target {float weight[3] = {0.4026, 0.2442, 0.0545};fixed3 sum = tex2D(_MainTex, i.uv[0]).rgb * weight[0];for (int it = 1; it < 3; it++) {sum += tex2D(_MainTex, i.uv[it*2-1]).rgb * weight[it];sum += tex2D(_MainTex, i.uv[it*2]).rgb * weight[it];}return fixed4(sum, 1.0);}// ---------------------------【轮廓图】---------------------------//Blur图和原图进行相减获得轮廓struct v2f_cull{float4 pos : SV_POSITION;half2 uv: TEXCOORD0;};v2f_cull vert_cull(appdata_img v){v2f_cull o;o.pos = UnityObjectToClipPos(v.vertex);o.uv = v.texcoord.xy;//dx中纹理从左上角为初始坐标，需要反向//通过判断_MainTex_TexelSize.y是否小于0来检验是否开启了抗体锯齿#if UNITY_UV_STARTS_AT_TOPif (_MainTex_TexelSize.y < 0)o.uv.y = 1 - o.uv.y;#endifreturn o;}fixed4 frag_cull(v2f_cull i) : SV_Target{//取原始场景纹理进行采样fixed4 mainColor = tex2D(_MainTex, i.uv);//对blur之前的rt进行采样fixed4 srcColor = tex2D(_SrcTex, i.uv);//对blur后的纹理进行采样fixed4 blurColor = tex2D(_BlurTex, i.uv);//相减后得到轮廓图fixed4 outline = ( srcColor - blurColor) * _OutlineColor;//输出：blur部分为0的地方返回原始图像，否则为0，然后叠加描边fixed4 final = saturate(outline) + mainColor;return final;}ENDCG// No culling or depthCull Off ZWrite Off ZTest Always//垂直高斯模糊Pass {CGPROGRAM#pragma vertex vertBlurVertical #pragma fragment fragBlurENDCG }//水平高斯模糊Pass {CGPROGRAM #pragma vertex vertBlurHorizontal #pragma fragment fragBlurENDCG}//轮廓图Pass {CGPROGRAM #pragma vertex vert_cull #pragma fragment frag_cullENDCG}}FallBack "Diffuse"}
C#：PostEffectsBase基类可以参考这里
using System.Collections;using UnityEngine;//编辑状态下也运行 [ExecuteInEditMode]//继承自PostEffectsbasepublic class OutLine : PostEffectsBase {//主相机private Camera mainCamera = null;//渲染纹理private RenderTexture renderTexture = null;private Material _material = null;/// 辅助摄像机 public Camera outlineCamera;// 纯色shaderpublic Shader purecolorShader;//描边处理的shaderpublic Shader shader;//迭代次数[Range (0, 4)]public int iterations = 3;//模糊扩散范围[Range (0.2f, 3.0f)]public float blurSpread = 0.6f;private int downSample = 1;public Color outlineColor = new Color (1, 1, 1, 1);public Material outlineMaterial {get {_material = CheckShaderAndCreateMaterial (shader, _material);return _material;}}void Awake () {mainCamera = GetComponent<Camera> ();if (mainCamera == null)return;createPurecolorRenderTexture ();}// ---------------------------【创建一个RenderTexture】---------------------------private void createPurecolorRenderTexture () {outlineCamera.cullingMask = 1 << LayerMask.NameToLayer ("Player");int width = outlineCamera.pixelWidth >> downSample;int height = outlineCamera.pixelHeight >> downSample;renderTexture = RenderTexture.GetTemporary (width, height, 0);}// ---------------------------【渲染之前调用】---------------------------private void OnPreRender () {if (outlineCamera.enabled) {//设置创建好的RenderTextureoutlineCamera.targetTexture = renderTexture;//渲染了一张纯色RenderTextureoutlineCamera.RenderWithShader (purecolorShader, "");}}//-------------------------------------【OnRenderImage函数】------------------------------------ // 说明：此函数在当完成所有渲染图片后被调用，用来渲染图片后期效果//-------------------------------------------------------------------------------------------------------- private void OnRenderImage (RenderTexture source, RenderTexture destination) {int rtW = source.width >> downSample;int rtH = source.height >> downSample;var temp1 = RenderTexture.GetTemporary (rtW, rtH, 0);var temp2 = RenderTexture.GetTemporary (rtW, rtH, 0);// 高斯模糊处理Graphics.Blit (renderTexture, temp1);for (int i = 0; i < iterations; i++) {outlineMaterial.SetFloat ("_BlurSize", 1.0f + i * blurSpread);//垂直高斯模糊Graphics.Blit (temp1, temp2, outlineMaterial, 0);//水平高斯模糊Graphics.Blit (temp2, temp1, outlineMaterial, 1);}//用模糊图和原始图计算出轮廓图outlineMaterial.SetColor ("_OutlineColor", outlineColor);outlineMaterial.SetTexture ("_BlurTex", temp1);outlineMaterial.SetTexture ("_SrcTex", renderTexture);Graphics.Blit (source, destination, outlineMaterial, 2);}}
参考
《Unity Shader 入门精要》
/puppet_master/article/details/54000951
